Efficient and sustained inhibition of ammonia nitrogen release from sediment in water by microbial self-aggregation zeolite layer.

Despite global efforts to manage water eutrophication, the continual release of ammonia nitrogen from sediments maintains the eutrophic state of water bodies, presenting serious challenges to the management. In order to find an efficient method for sediment remediation, the experiment of using signal molecules to enhance the adhesion of microorganisms on zeolite was carried out. Five different zeolitic ammonium adsorptions were examined using two different signal molecules, N-(3-oxohexanoyl)-L-homoserine lactone (OHHL) and N-(ß-ketocaproyl)-DL-homoserine lactone (C6), to enhance microbial attachment on two types of zeolites. The results showed that the modified microbial attached Z1 zeolite reinforced with signal molecule C6 had the best effect. The effect was better in the case of high ammonium adsorption, and the TN removal could reach 7.99 mg·L-1 with an inhibition rate of 90.08%. The ammonia nitrogen removal reached 4.75 mg·L-1 with an inhibition rate of 87.64%, and the ammonia nitrogen and total nitrogen of the overlying water reached the surface III water quality standard. In addition, the addition of the signal molecule increased the zeta potential on the surface of the bacterial colloid. In addition, the amount of protein I in the dissolved organic matter (DOM) fraction increased, improving microbial adhesion ability and facilitating their attachment to the zeolite surface. The signal molecule C6 could increase the zeta potential of microbial surface and promote the production of protein I, thus strengthening the attachment of zeolite biofilm and improving the water quality.

A study on the simultaneous determination of nitrogen content and 15N isotope abundance in plants using peak height intensities at m/z 28 and 29.

A method for simultaneous determination of nitrogen content and 15N isotope abundance in plants was established by Elemental analysis-gas isotope ratio mass spectrometry. Taking poplar leaves and l-glutamic acid as standards, nitrogen content was determined using the standard curve established by weighted least squares regression between the mass of nitrogen element and the total peak height intensity at m/z 28 and 29. Then the 15N isotope abundance was calculated with the peak height intensity at m/z 28 and 29. Through the comparison of several sets of experiments, the impact of mass discrimination effect, tin capsule consumables, isotope memory effect, and the quality of nitrogen on the results were assessed. The results showed that with a weight of 1/x2, the standard curve has a coefficient of determination (R2) of 0.9996. Compared to the traditional Kjeldahl method, the measured nitrogen content deviated less than 0.2 %, and the standard deviation (SD) was less than 0.2 %. Compared to the sodium hypobromite method, the 15N isotopic abundances differed less than 0.2 atom%15N, and the SD was less than 0.2 atom% 15N. The established method offers the advantages of being fast, simple, accurate, and high throughput, providing a novel approach for the simultaneous determination of nitrogen content and 15N isotope abundance in plant samples.

Study on the mechanism promoting oxidation of long-chain alkanes by self-produced surfactant-like substance at the solid-liquid interface.

The Fenton method to remediate oil-contaminated soils has long suffered from low utilization of ·OH, resulting in waste of costs during practical application. This study investigated the efficient utilization of ·OH in oxidation using three different soils contaminated with oil (S1, S2, and S3). The mechanisms of promoting oxidation of long-chain alkanes by self-produced surfactant-like substance at the solid-liquid interface were studied. These results (take S1 as an example) showed that the average ·OH utilization rate of oxidized long-chain alkanes (Ka) at the solid-liquid interface reached 88.34 (mg/kg∙(a.u.)), which was higher than the non-solid-liquid interface stage (I: 54.02 (mg/kg∙(a.u.)), II: 67.36 (mg/kg∙(a.u.))). Meanwhile, the average oxidation of long-chain alkanes could increase unit ·OH intensity added (Kb) in the solid-liquid interface (990.00 mg/kg), which was much higher than Kb of the non-solid-liquid interface stage (I: 228.34 mg/kg, II: -1.48 mg/kg). Furthermore, there was a significant correlation between the proportion of humic acid-like in soil organic matter and the oxidation of long-chain alkanes at the solid-liquid interface. Thus, the surfactant-like substance generated during oxidation promoted the oxidation of long-chain alkanes at the solid-liquid interface. Moreover, when the surfactant-like substance had a matching degree (φ) with the long-chain alkanes (S1 0.18, S2 0.15, and S3 0.25), the efficiency of the ·OH utilization reached the peak, and the direct oxidation of long-chain alkanes at the solid-liquid interface was finally achieved (S1: 1373.00 mg/kg, S2: 1473.18 mg/kg, and S3: 1034.37 mg/kg). The appropriate surfactant-like substance agents in the construction can reduce the dosing of H2O2 and the construction costs by improving the efficient utilization of ·OH. Study on the mechanism promoting oxidation of long-chain alkanes by self-produced surfactant-like substance at the solid-liquid interface.

Rapid degradation of long-alkanes by mild Fe-SOM pre-oxidation in soils.

In this study, a novel mild pre-oxidation mode was successfully explored by fabricating Fe-SOM prepared by adding 2.5% and 20% fulvic acid (FA). This study explored the mechanism of mild Fe-SOM pre-oxidation to stimulate rapid biological degradation of long-alkanes in oil-contaminated soils. Results showed that under mild Fe-SOM pre-oxidation, the total •OH intensity and bacterial killing degree（D） were low, and hydrocarbon conversion（C）was fast, resulting in rapid degradation of long-alkanes. Additionally, the fast group removed 1.7-fold more than slow group and biodegraded long-alkanes 182 days significantly faster. Furthermore, compared with slow group (8.26 log CFU/g), the fast group (51.48 log CFU/g) characterized much more bacteria. Besides, the fast group had higher C (5.72%-15.95%), thus increasing the degradation rate of long-alkanes (7.61%-18.86%). A shift in the microbial community was found after mild Fe-SOM pre-oxidation, with an average relative abundance of 18.6% for the dominant genus Bacillus. Therefore, the mild pre-oxidation reduced the D, and the high bacterial abundance promoted nutrients consumption and C, which shortened bioremediation period and increased the long-alkanes degradation rate. This study provided a promising novel mild Fenton pre-oxidation mode to rapid remediate heavily multicomponent oil-contaminated soils.

Fast degradation of macro alkanes through activating indigenous bacteria using biosurfactants produced by Burkholderia sp.

Soil bacteria that produce biosurfactants can use total petroleum hydrocarbons (TPHs) as a carbon source. This study demonstrated that biosurfactants produced by Burkholderia sp. enhanced the recovery and synergism of soil microbial community, resulting in fast degradation of macro alkanes. Experiments were carried out by applying bio-stimulation after pre-oxidation to investigate the effects of nutrient addition on biosurfactant production, TPH degradation, and microbial community succession in the soil. The results presented that bio-stimulation could produce biosurfactants in high C/N (32.6) and C/H (13.3) conversion after pre-oxidation and increased the total removal rate of TPH (10.59-46.71%). The number of total bacteria had a rapid increase trend (2.94-8.50 Log CFU/g soil). The degradation rates of macro alkanes showed a 4.0-fold (48.07 mg/kg·d-1 versus 186.48 mg/kg·d-1) increase, and the bioremediation time of degrading macro alkanes saved 166 days. Further characterization revealed that the biosurfactants produced by Burkholderia sp. could activate indigenous bacteria to degrade macro alkanes rapidly. A shift in phylum from Actinomycetes to Proteobacteria was observed during bioremediation. The average relative abundance of the microbial community increased from 36.24 to 64.96%, and the predominant genus tended to convert from Allorhizobium (8.57%) to Burkholderia (15.95%) and Bacillus (15.70%). The co-occurrence network and Pearson correlation analysis suggested that the synergism of microbial community was the main reason for the fast degradation of macro alkanes in petroleum-contaminated soils. Overall, this study indicated the potential of the biosurfactants to activate and enhance the recovery of indigenous bacteria after pre-oxidation, which was an effective method to remediate petroleum-contaminated soils.

Insight on efficiently oriented oxidation of petroleum hydrocarbons by redistribution of oxidant through inactivation of soil organic matter coupled with passivation of manganese minerals.

While extensive works focused on the enhancement of the activity of heterogeneous Fenton catalysts, little was paid attention to the inhibition of soil organic matter (SOM) and Mn minerals in soil remediation. Here, the oxidation of petroleum hydrocarbons in soils (S1: 4.28 % SOM, S2: 6.04 % SOM, S3: 10.33 % SOM) with inactivated SOM and passivated Mn oxides regulating by calcium superphosphate (Ca(H2PO4)2) was carried out. Oily sludge pyrolysis residue was used as precursors to prepare an oleophilic iron-supported solid catalyst (Fe-N @ PR). For regulated systems, under the optimal conditions of 1.8 mmol/g H2O2 and 0.05 g/g Fe-N @ PR, 72 ∼ 91 % of total petroleum hydrocarbons (TPHs: 15,616.58 mg/kg) were oxidized, which was 38 ∼ 45 % higher than that of control systems. The mechanism of efficient oxidation was proposed that the passivated Mn minerals stabilized H2O2 redistributing more H2O2 to sustainably produce •OH, and the inactivated SOM improved the relative reactivity of •OH to TPHs. Additionally, the passivation of Mn oxides was mainly related to the binding of H2PO4-, and the inactivation of SOM was realized by Ca2+ combing with -OH and C-O-C to form stable complexes. This study brought us a new perspective on soil remediation through passivating Mn minerals and inactivating SOM.

Enhanced biological S0 accumulation by using signal molecules during simultaneous desulfurization and denitrification.

A high rate of elemental sulfur (S0) accumulation from sulfide-containing wastewater has great significance in terms of resource recovery and pollution control. This experimental study used Thiobacillus denitrificans and denitrifying bacteria incorporated with signal molecules (C6 and OHHL) for simultaneous sulfide (S2-) and nitrate (NO3-) removal in synthetic wastewater. Also, the effects on S0 accumulation due to changes in organic matter composition and bacteria proportion through signal molecules were analyzed. The 99.0% of S2- removal and 99.3% of NO3- was achieved with 66% of S0 accumulation under the active S2- removal group. The S0 accumulation, S2- and NO3- removal mainly occurred in 0-48 h. The S0 accumulation in the active S2- removal group was 2.0-6.3 times higher than the inactive S2- removal groups. In addition, S0/SO42- ratio exhibited that S0 conversion almost linearly increased with reaction time under the active S2- removal group. The proportion of Thiobacillus denitrificans and H+ consumption showed a positive correlation with S0 accumulation. However, a very high or low ratio of H+/S0 is not suitable for S0 accumulation. The signal molecules greatly increased the concentration of protein-I and protein-II, which resulted in the high proportion of Thiobacillus denitrificans. Therefore, high S0 accumulation was achieved as Thiobacillus denitrificans regulated the H+ consumption and electron transfer rate and provided suppressed oxygen environment. This technology is cost-effective and commercially applicable for recovering S0 from wastewater.

An updated systematic review and meta-analysis of fecal microbiota transplantation for the treatment of ulcerative colitis.

BACKGROUND: Fecal microbiota transplantation (FMT) as a promising therapy for ulcerative colitis (UC) remains controversial. We conducted a systematic review and meta-analysis to assess the efficiency and safety of FMT as a treatment for UC. METHODS: The target studies were identified by searching PubMed, EMBASE, the Cochrane Library, Web of Science, and ClinicalTrials and by manual supplementary retrieval. We conducted a general review and quantitative synthesis of included studies. We used the RevMan and Stata programs in the meta-analysis. The outcomes were total remission, clinical remission, steroid-free remission, and serious adverse events. We also performed subgroup analyses based on different populations. RESULTS: A total of 34 articles were included in the general review. Only 16 articles, including 4 randomized controlled trials, 2 controlled clinical trials, and 10 cohort studies, were selected for the meta-analysis. We found that donor FMT might be more effective than placebo for attaining total remission (risk ratio [RR]: 2.77, 95% confidence interval [CI]: 1.54-4.98; P = .0007), clinical remission (RR: 0.33, 95% CI: 0.24-0.41; P < .05), and steroid-free remission (RR: 3.63, 95% CI: 1.57-8.42; P = .003), but found no statistically significant difference in the incidence of serious adverse events (RR: 0.88, 95% CI: 0.34-2.31, P = .8). The subgroup analyses revealed significant differences between the pooled clinical remission rates for different regions, degrees of severity of the disease, and patients with steroid- or nonsteroid-dependent UC. CONCLUSIONS: FMT can achieve clinical remission and clinical response in patients with UC.

Efficient adsorption of dyes from aqueous solution using a novel functionalized magnetic biochar: Synthesis, kinetics, isotherms, adsorption mechanism, and reusability.

In this study, a novel adsorbent, dodecylbenzene sulfonic acid (DBSA) functionalized magnetic biochar (DBSA-Fe3O4@BC), was synthesized and used to efficiently remove dyes from aqueous solution. The results indicated that DBSA-Fe3O4@BC exhibited an excellent adsorption capacity for Rhodamine B (RhB), and the maximum adsorption capacity for RhB at 298 K was 367.67 mg/g, which was approximately 2.3-1.2 folds than that of BC, dodecylsulfonic acid functionalized biochar (DSA@BC), DBSA@BC, Fe3O4@BC, and DSA-Fe3O4@BC. The possible adsorption mechanisms for RhB adsorption by DBSA-Fe3O4@BC included pore filling, electrostatic attraction, H bond, and surface complexation. Importantly, structural control presented that the simultaneous introduction of alkyl and phenyl groups significantly enhanced RhB adsorption by DBSA-Fe3O4@BC through hydrophobic and π-π interaction. Combined ethanol (EtOH) desorption and H2O2 oxidation regeneration, DBSA-Fe3O4@BC remained high-performance for RhB adsorption after six cycles (97.44%), indicating its outstanding reusability. In summary, DBSA-Fe3O4@BC exhibited a prospective application for dyeing wastewater treatment.

Efficient catalytic degradation of alkanes in soil by a novel heterogeneous Fenton catalyst of functionalized magnetic biochar.

In this study, sodium dodecyl sulfate (SDS) functionalized magnetic biochar (SDS-Fe@BC) was successfully prepared. Compared to other traditional heterogeneous Fenton catalysts, more total petroleum hydrocarbons (TPH) (3499.40 mg kg-1) was adsorbed from soil to the surface of SDS-Fe@BC through hydrophobic interaction between alkyls in alkanes and SDS-Fe@BC, which formed an efficient interface oxidation system. In SDS-Fe@BC-mediated heterogeneous Fenton system, 10,191.41 mg kg-1 (88.10%) TPH was degraded in the presence of 400 mM H2O2, which was 1.38-5.67 folds than that of H2O2 alone, Fe2+, zero valent iron (ZVI), Fe3O4, pristine biochar (BC), and Fe@BC. Moreover, all individual alkanes were efficiently degraded (>75%), and the higher the initial amount of individual alkane, the more the degradative amount in the SDS-Fe@BC/H2O2 system. Additionally, TPH degradation was highly related to the mass ratio of SDS/Fe@BC, H2O2 concentration, SDS-Fe@BC dosage, and initial pH in the SDS-Fe@BC/H2O2 system, and the optimal values were 1:5, 400 mM, 50 mg g-1, and pH 7, respectively. Radical quenching experiments revealed that hydroxyl radicals (•OH) generated on the surface of SDS-Fe@BC was the dominated reactive oxidative species (ROS) responsible for alkanes degradation. After five cycles, SDS-Fe@BC still remained a high catalytic activity for alkanes degradation (73.21%), showing its excellent reusability. This study proved that the SDS-Fe@BC can be used as a potential heterogeneous Fenton catalyst for petroleum-contaminated soil remediation.

Mechanistic insight into cost-effective dedicated oxidation of alkanes by inactivating soil organic matter with FeOOH formed in situ.

Modified Fenton technique has been widely used to remediate soils contaminated with crude oil but significantly limited to soil organic matter (SOM) consuming oxidants. In this study, soils with developed SOM inactivation by FeOOH formed in situ were created and spiked with crude oil (total petroleum hydrocarbons (TPH): 19453 mg/kg), then treated by modified Fenton reagents. The reaction activity of hydroxyl radicals (•OH) relative to TPH (K) notably increased to 0.65 when the degree of developed inactivation of the SOM (ß) was 100% (DIS-100), which was 1.45, 2.03 and 2.83-fold than that of DIS-50, DIS-15 and control (CK), respectively. Meanwhile, the higher the K, the more •OH transferred, which realized the efficient oriented oxidation of TPH. Moreover, improving the transfer of •OH from SOM to TPH was more important than increasing •OH production in soil remediation. With the ß increasing to 100%, the ratio of invalid H2O2 decomposition to produce O2 decreased to 22%, equal to 25% reduction compared to CK. Therefore, when ß was 100%, the utilization efficiency of H2O2 was improved to 1.48 mg/mmol, which was approximately 1.39, 3.35 and 5.43-fold higher than the efficiency got by DIS-50, DIS-15 and CK, respectively, achieving the cost-effective dedicated oxidation of TPH. In addition, the FeOOH cross-linked with SOM via Fe-O-C and Fe-N bonds to develop inactivation of SOM. In general, this study highlighted a new insight into the effect of developed inactivation of SOM on soil remediation.

Efficient removal of heavily oil-contaminated soil using a combination of fenton pre-oxidation with biostimulated iron and bioremediation.

Crude oil contamination severely deteriorates soils quality. Bioremediation utilizing soil indigenous organisms could be employed to decompose petroleum hydrocarbons thanks to its low cost and minor environmental disturbance. However, slow kinetics limit the successful application of this biotechnique. Pretreating oil-contaminated soils with Fenton pre-oxidation could accelerate the subsequent bioremediation process. This study was to explore the mechanisms behind the rapid propagation of indigenous petroleum-degrading bacteria (IPDB) and the efficient degradation of total petroleum hydrocarbons (TPH) in soil after Fenton pre-oxidation with biostimulated iron. Biostimulated iron and non-biostimulated iron were used in the experiments, where Fenton pre-oxidation was combined with the bioremediation of oil-contaminated soil (TPH = 13221 mg/kg). Although the amount of Fenton pre-oxidized TPH (3331-3775 mg/kg) was similar with biostimulated and non-biostimulated irons, the biodegradation of TPH after Fenton pre-oxidation with biostimulated iron (5840 mg/kg) was much higher than that with non-biostimulated iron (3034-4034 mg/kg). Moreover, abundant nutrients and a high population of residual IPDB were found after Fenton pre-oxidation with biostimulated iron, which benefited stable consumption of NH3-N and dissolved organic carbon (DOC) by IPDB during the subsequent bioremediation. However, Fenton pre-oxidation with non-biostimulated iron either resulted in greater damage to IPDB or produced fewer nutrients, thereby failing to ensure the continuous propagation of IPDB during the subsequent bioremediation. Therefore, we propose that Fenton pre-oxidation with biostimulated iron should be applied to heavily oil-contaminated soils prior to bioremediation.

Rapid and efficient adsorption of tetracycline from aqueous solution in a wide pH range by using iron and aminoacetic acid sequentially modified hierarchical porous biochar.

The object of this work was to synthesize an iron and aminoacetic acid sequentially modified hierarchical porous biochar (AC-Fe@HPBC) for tetracycline (TC) removal from aqueous solution. Results showed that AC-Fe@HPBC had a larger surface area (362.5370 m2/g), developed microporous structure (0.1802 cm3/g), and numerous functional groups, which provided more adsorption sites. The maximum adsorption capacity towards TC by AC-Fe@HPBC was 457.85 mg/g, 1.43, 1.29 and 1.20-fold than that of HPBC, AC@PHBC and Fe@HPBC, respectively, and the super-fast adsorptive equilibrium was achieved within 10 min. Additionally, introducing amino and carboxyl functional groups on the AC-Fe@HPBC surface significantly broadened the operation pH range (3-11). Site energy analysis indicated TC and AC-Fe@HPBC had stronger adsorption affinity at a higher temperature. The adsorption mechanism involved pore filling, surface complexation, H-bond and π-π interaction. Moreover, the reusability experiments proved AC-Fe@HPBC as an effective adsorbent for TC removal from aqueous solution.

[Persistent Inhibition of Ammonium Released from Contaminated Sediments Through a Modified Zeolite and Biofilm System Enhanced by Signaling Molecules].

This experiment used a modified zeolite and biofilm system to find a long-term effective way of repairing sediment. Four types of modified zeolites[AlCl3, Al(NO3)3, Al2(SO4)3, and KAl(SO4)2] and a biofilm system were investigated for the removal of ammonia nitrogen from overlaying water. The results showed that, of the modified zeolites, AlCl3 had the greatest effect on the zeolite and biofilm system, and the optimal modified concentration was 0.8 mol·L-1. The persistence was further studied after adding OHHL, including the inhibition of ammonium released from contaminated sediment by the AlCl3-modified zeolite and biofilm system, NaCl-modified zeolite and biofilm system, and natural zeolite and biofilm system. The results illuminated that the number of bacteria attached to the AlCl3-modified zeolite and biofilm system was the highest, and the proportion of denitrifying bacteria was also high (the initial proportion was 82.1%; 30 days later it was 61.1%). Therefore, the biological regeneration was high (64.9%), which caused the zeolite service life to be up to 8.5 months. Thus, ammonium released from contaminated sediment can be inhibited effectively and continuously by an AlCl3-modified zeolite and biofilm system.

Regulating intermediates to realize the coupled hydrion with biology polysulfide in wastewater treatment.

The purpose of this study is to clarify the mechanism of the coupled hydrion with biology polysulfide in the simultaneous denitrification and desulfurization process. The coupled hydrion with biology polysulfide, uncoupled hydrion with biology polysulfide and no polysulfide experiments were performed in wastewater with two kinds of sulfide loads (100 and 200 mg/L). When the concentration of thiosulfate was suitable, the free H+ concentration (74.2 and 91.0 mg/L) and the proportion of Thiobacillus denitrificans (85.4% and 59.7%) were both higher under the two kinds of sulfide loading conditions (100 and 200 mg/L), and coupled hydrion with biology polysulfide was realized (the production of elemental sulfur is as high as 33 and 101 mg/L). Further analysis shown that the way of coupled hydrion with biology polysulfide were both: 2.0S2-+6.4NO3-+30.1H++21.7e-→1.0S2-+1.0SO42-+3.2N2+15.0H2O. In addition, for the coupled hydrion with biology polysulfide, more nitrates could be utilized to produce elemental sulfur S0, and the lower ratio of H+/S0 and SO42-/S0 were observed (S2- = 100 mg/L: 2.3 and 0.9; S2- = 200 mg/L: 0.9 and 0.03), which could promote the growth of Thiobacillus denitrificans and increase the proportion of Thiobacillus denitrificans. This maybe one of the reasons why coupled hydrion with biology polysulfide could be achieved.

Fast biodegradation of long-alkanes by enhancing bacteria performance rate by per-oxidation.

The long-alkanes biodegradation rate was generally found slow during widely used pre-oxidation combined with biodegradation for oil contamination treatment, resulting in long and unsustainable removal. In this study, different chitosan content was used to produce iron catalysts for pre-oxidation, and nutrients were added for the long-alkanes biodegradation experiment. Mechanism of Fenton pre-oxidation and improvement in the biodegradation rate of long-alkanes were studied by analyzing the change in organic matter and bacterial community structure, the amount and activity of bacteria in the biological stage, and the degradation amount long-alkanes hydrocarbon before and after pre-oxidation. Results showed that the destruction of bacteria greatly reduced when hydroxyl radical intensity decreased to 4.40 a.u.. Also, the proportion of humic acid-like was high (40.88%), and the community structure was slightly changed with the pre-oxidation for the fast biodegradation (FB) group. In the subsequent biodegradation, it was found that the degradation rate of each long-alkanes in the FB group increased significantly (C30: 4.18-8.32 mg/(kg·d)) with the increase of the degradation of long-alkanes (10-50%). Further studies showed that the high nutrient dynamics (6.05 mg/(kg·d)) of the FB group resulted in high bacteria performance rate (0.53 mol CO2 × log CFU/(104 g2 d)), which further accelerated the substrate transformation(41%). Therefore, the biodegradation rate of long-alkanes was increased (43.8 mg/(kg·d)) with the removal rate of long-alkanes of 76%. The half-life of long-alkanes for the FB group (64 d) was 33 d shorter than the slow biodegradation group (99 d). These results exhibited that pre-oxidation regulation can shorten the bioremediation cycle by improving the biodegradation rate of long-alkanes. This research has good engineering application value.

Efficient cyclic oxidation of macro long-chain alkanes in soil using Fenton oxidation with recyclable Fe.

Recyclable Fe in soil was prepared by using fermented food waste supernatant. The efficient cyclic oxidation of long-chain alkanes in oil-contaminated soils could be achieved by Fenton oxidation with the recyclable Fe. The oxidation efficiency of macro long-chain alkanes (C27-C30) from the first cycle (63.4%) to the last cycle (60.1%) showed no significant decrease during three-cycle Fenton oxidation with the recyclable Fe. However, for the oil-absorbing Fe prepared by HA and Fe-SOM prepared by Cs, the oxidation efficiency of C27-C30 could not be efficiently cyclic oxidized during three-cycle Fenton oxidation. Further analysis showed that the proportion of Fe(III) in the recyclable Fe was higher than that in the oil-absorbing Fe or the Fe-SOM, where the iron content was similar. Moreover, more fulvic-like acid and humic-like acid were found in the recyclable Fe, and thus many Fe(III) ions simultaneously combined with the fulvic-like acid and humic-like acid through -C-O-C and CË­O bonds in the recyclable Fe. It was the recyclable Fe with such a stable structure that could still maintain high catalytic activity and efficiently cyclic oxidize macro long-chain alkanes during three-cycle Fenton oxidation, which is valuable for its repeated use.

Stimulated biodegradation of all alkanes in soil.

This study aim to investigate the biodegradation of all alkanes in soil by adding stimulater and indigenous bacteria. The experiments were carried out by adding native bacteria and the stimulater to the soil S1 (total petroleum hydrocarbon (TPH) = 22,745 mg/kg) and soil S2 (TPH = 13,833 mg/kg) to explored the effect and mechanism of the stimulated biodegradation of all alkanes in soil. The results showed that most alkanes were used as the main carbon source of TPH in the late stimulation stage, so that all alkanes could be biodegraded by stimulating. The biodegradation of C10 - C19 (4527 mg/kg) and C20 - C30 (8530 mg/kg) were much higher than the stimulated biodegradation of partial alkanes, which indicated that the biodegradation effect of TPH was greatly improved. In addition, for the stimulated biodegradation of all alkanes group, the relative activity of TPH (TPH biodegradation/DOC consumption) was nearly 5 times that of the stimulated biodegradation of partial alkanes group in the late stimulation stage. The amount of ammonia allocated to TPH in the late stimulation stage was nearly 10 times that of DOC, and the organic matter components changed greatly in the early stimulation stage, but there was basically no change in the later stage. It showed that the hydrocarbon degraders in the stimulated biodegradation of all alkanes group used DOC as the main carbon source in the early stimulation stage and mainly degrade TPH in the later stage, which improved the biodegradation efficiency of petroleum hydrocarbons.

[Effect of Artificial Mixing on Temporal and Spatial Succession of Algae Community Structure in Jinpen Reservoir].

To explore the effect mechanism of the artificial mixing process on the temporal and spatial succession of algae community structure in a water body, this study used water-lifting aerators to induce in-situ artificial mixing of the water body of Jinpen Reservoir, and in-situ spot physical-chemical parameters and algae of the water body of the reservoir were observed during an artificial mixing process. A total of 51 species of 28 genera of 6 families of algae were identified in the water body of the Jinpen Reservoir. The artificial mixing effect of the water-lifting aerators significantly inhibited the growth of algae in the water, and had a significant impact on the community structure. Before activation of the water-lifting aerators, algae were mainly distributed in the surface water body, and Chlorella vulgaris was the dominant species. With the operation of the water-lifting aerators, the algal density of surface water body decreased significantly, and the vertical distribution of the algae density in the water body tended to be uniform. The dominant species tended to succeed in Cyclotella sp. This study used the method of redundancy analysis, combined with critical depth theory and the characteristics of algae growth, to analyze the relationship between the spatial-temporal succession of algae community structure and the changes in the main physical-chemical parameters in Jinpen Reservoir during the artificial process. The analysis results showed that the artificial mixing of the water-lifting aerators mainly affects the temporal and spatial succession of the algae community structure by rapidly destroying the thermal stratification stability of the water body and significantly increasing the water mixing depth.

Oriented oxidation of all alkanes in soils.

In order to investigate the mechanism of the oriented oxidation of all alkanes by regulating organic functional groups, Fenton oxidation was performed in two soils (S1 and S2: total petroleum hydrocarbons (TPH) are 26,281 mg/kg and 12,668 mg/kg). The higher the proportion of hydroxyl radicals (OH) transferred (41 %-58 %), the more the number of oriented oxidation of alkanes, which realized the oriented oxidation of all alkanes. Meanwhile, high oriented oxidation of long alkanes and short alkanes (58 %: 3405 mg/kg and 1729 mg/kg) was observed. Protein Ⅰ in soil organic matter (SOM) was reduced by regulating CH and carboxyl group OH, which indicated that protein Ⅰ was inactive. Protein Ⅰ oxidation after regulation was decreased significantly. Protein Ⅰ was the main active organic matter to capture OH. When the relative reactivity coefficient KTPH/SOM (the ratio of TPH oxidation to SOM oxidation) and KTPH/protein I (the ratio of TPH oxidation to protein Ⅰ oxidation) were higher than 1, low oxidation of SOM and protein Ⅰ was obtained. It indicated that for the oriented oxidation of all alkanes, the high coefficient of relative reactivity for petroleum was the key for the transfer of OH from oxidizing SOM to oxidizing alkanes.